A heavy duty belt laying work machine includes a frame, a driver wheel mounted in supporting relation to the frame on each lateral side thereof, an idler wheel assembly disposed on each lateral side of the frame. The idler wheel assembly includes an idler wheel and a carry-roller, each of which is rotatably connected to an idler support arm that is pivotally mounted in supporting relation to the frame. A mid-roller is disposed on each lateral side of the frame between the driver wheel and the idler wheel assembly and rotatably connected to a mid-roller support arm mounted in supporting relation to the frame. An endless, inextensible belt is entrained about each respective idler wheel and driver wheel on each lateral side of the frame and contacts the mid-roller and the carry-roller. Apparatus are provided for controllably tensioning and urging each belt into frictional driven engagement with a corresponding one of the driver wheels
